Imre Deak 9069b77545 drm/i915/dp_mst: Fix PBN / MTP_TU size calculation for UHBR rates
Atm the allocated MST PBN value is calculated from the TU size (number
of allocated MTP slots) as

  PBN = TU * pbn_div

pbn_div being the link BW for each MTP slot. For DP 1.4 link rates this
worked, as pbn_div there is guraranteed to be an integer number, however
on UHBR this isn't the case. To get a PBN, TU pair where TU is a
properly rounded-up value covering all the BW corresponding to PBN,
calculate first PBN and from PBN the TU value.

Calculate PBN directly from the effective pixel data rate, instead of
calculating it indirectly from the corresponding TU and pbn_div values
(which are in turn derived from the pixel data rate and BW overhead).

Add a helper function to calculate the effective data rate, also adding
a note that callers of intel_dp_link_required() may also need to check
the effective data rate (vs. the data rate w/o the BW overhead).

While at it add a note to check if WA#14013163432 is applicable.

v2:
- Fix PBN calculation, deriving it from the effective data rate directly
  instead of using the indirect TU and pbn_div values for this.
- Add a note about WA#14013163432. (Arun)
v3:
- Fix rounding up quotient while calculating remote_tu. (Ville)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Arun R Murthy <arun.r.murthy@intel.com> (v1)
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231117150929.1767227-3-imre.deak@intel.com
2023-11-21 16:32:44 +02:00
2022-09-28 09:02:20 +02:00
2023-09-17 14:40:24 -07:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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